Intestinal epithelial cell (IEC) apoptosis often occurs in severe surgical conditions such as hemorrhagic shock, severe trauma, sepsis, septic shock, and neonatal necrotizing enterocolitis (NEC). Recent evidence suggests that IEC apoptosis is a critical pathogenic event for development of NEC, a severe neonatal surgical disease characterized by inflammation and segmental coagulative bowel necrosis. However, it remains unknown how IEC apoptosis causes coagulative bowel necrosis. In preliminary studies, we created a novel 3xTg-iEAP transgenic mouse line that can develop scattered crypt IEC apoptosis via inducibly expressing a transgene coding a NEC-associated apoptosis inducer in IEC specific manner. Using adult 3xTg-iEAP mice, we found that induction of scattered crypt IEC apoptosis subsequently causes segmental intestinal villus necrosis and systemic inflammation that mimic clinical and pathological aspects of human NEC, strongly supporting the notion that scattered IEC apoptosis is a pathogenic factor for NEC. Furthermore, we obtained preliminary data that lead to the novel hypothesis that scattered crypt IEC apoptosis is a pivotal event that triggers IFN-?-mediated sensitizing IECs to programmed necrosis, thus in turn turning on the ?motor? of necrotizing intestinal inflammation. To prove this hypothesis, we will execute three complementary Specific Aims: (1) We will examine if induction of scattered IEC apoptosis directly initiates NEC in neonatal 3xTg-iEAP mice (P1 ? P5), define pathology and pathophysiology of scattered IEC apoptosis-induced neonatal intestinal inflammatory injury and verify key findings by comparing them to that derived from a classic neonatal mouse NEC model. We will further examine if major risk factors of NEC enhance susceptibility of neonatal 3xTg-iEAP mice to scattered IEC apoptosis-induced NEC-like intestinal injury. (2) We will test the hypothesis that IFN-? induced by either crypt IEC apoptosis or NEC stress challenge up-regulates a key regulator for programmed necrosis in villus IECs, which subsequently mediates necrosis and disruption of bowel tissue by neutrophils and neutrophil-derived oxidants in neonates. Specifically, we will study whether and how interactions among these events and factors contribute to the pathogenesis of neonatal necrotizing intestinal inflammation through utilizing multidisciplinary approaches that are incorporated with techniques of cell biology, molecular biology, physiology, and mouse genetic engineering. (3) We will study the exact role of regulators for programmed necrosis in development of neonatal necrotizing intestinal inflammation triggered by either scattered IEC apoptosis or NEC stresses. We will achieve this aim using in vivo and in vitro approaches involving molecular biology and mouse genetic engineering techniques. We expect that this project will yield a novel animal model for studying molecular mechanisms and pathophysiology of gut injury-associated critical surgical illness, provide insights about how scattered IEC apoptosis contributes to development of severe surgical conditions such as NEC and sepsis, and advance our knowledge on new approaches in preventions and treatment of critical surgical illness.